Display devices using a touch panel as an input device are widely used in portable information terminals, for example. For example, JP 2009-303209 A discloses a portable communication terminal that displays, in an image display region, image data generated by a camera, generates touch data in response to input by a contact in a touch region mounted at the image display region, and stores the generated touch data together with the image data. When the image data is presented, this portable communication terminal enables display of touch data, such as a character or drawing, at the time of entry of touch data.
In recent years, along with increasingly advanced functionality of portable information terminals, the range of services that can be used on a portable information terminal has expanded. For example, a shopping site may be accessed on a portable information device to purchase goods, or various services by financial institutions, such as banks, may be used. In this context, to prevent an unauthorized user from using a portable information terminal, providing restrictions on the use or operation thereof by means of personal authentication has gained importance.